You didn’t say what your application method was, but that can be solved with a pad soaked in some DNA. Working the pad around the surface will redissolve the shellac and the pad should re distribute it more evenly. I’ve used a lot of shellac, and I still can’t brush it very well. I have to ether pad it or spray it. I do thick the Zinnser is pretty thick to work with, and I always cut it back a little with DNA. Another problem may be the temps…outside on a hot day is just going to make it that much harder to work out into an even coat. If you are brushing, the common advice is to only brush it once, do not go back and forth, apply the finish with just slightly overlapping brush strokes. But like I said, I can’t brush it.